1. Field of the Invention
The present invention relates to a multibeam laser diode radiating a plurality of laser lights from one light emitting device.
2. Description of the Related Art
In a multibeam laser diode, junction-down assembly advantageous to heat release is desirable. However, in the case where the beam interval is small, the width of the electrode and the width of the solder layer become small, and junction-down assembly is hardly realized because of the following reason. That is, in junction-down assembly, a contact electrode in a state of stripe is provided on the device side, and a solder layer in a state of stripe similar to that on the device side is provided on the submount (support) side. By jointing the contact electrode to the solder layer, electric contact is obtained. In this method, depending on mounting precision in solder joint, for example, the following concerns exist: 1. leakage; 2. deterioration of heat release characteristics; and 3. nonuniform solder joint stress is applied to the stripe.
“1. leakage” is generated in the case where in jointing, the solder extends over the next contact electrode. Such leakage becomes a large disadvantage as the pitch becomes smaller or the number of beams becomes larger. “2. deterioration of heat release characteristics” is caused by difference of solder joint state between beams. As the width of the electrode and the width of the solder layer become smaller, the tolerance range of mounting precision becomes smaller. Thus, if the mounting position is shifted even slightly, joint state with the solder differs according to each beam. “3. nonuniform solder joint stress is applied to the stripe” is also caused by mounting position shift. If the solder is jointed while position shift with respect to the stripe is left, nonuniform joint stress is applied to the stripe, which affects polarization characteristics and reliability.
To resolve the foregoing disadvantages, for example, in Japanese Unexamined Patent Application Publication No. 2000-269601, the following structure is disclosed. In the structure, in the case of junction-up assembly, by providing a high-resistivity isolation region between light emitting devices of a multibeam laser diode equipment, short circuit between the light emitting devices due to destruction of an interlayer insulating film in bonding is prevented. Further, for example, in Japanese Unexamined Patent Application Publication No. 2006-24665, the following structure is disclosed. In the structure, in the case of junction-down assembly, an insulating film is formed on a first electrode covering stripe, a second electrode is formed in an aperture provided in the insulating film, and thereby the first electrode and the second electrode are electrically connected, and the second electrode is jointed to a submount by solder.